Last year, I got into road cycling. Because of this, I acquired a smart bike trainer (you attach it to your bike and apps can control its resistance via Bluetooth). I tried a couple of apps but quickly became bored. I feel they are mostly focused on either online racing or a serious structured training. I'm not really interested in these.

My favorite part of cycling are cycling trips. You go to some destination and try to complete the world-known routes and climbs. I thought to myself that I would love to somehow replicate this with my bike trainer. A way to have a clear progression, challenge, and no repetition.

To sum up, I wanted to have:

- Real-world terrains and routes

- Clear progression

- A sense of accomplishment from completing a challenging route

- No aids like decreasing grade difficulty or skipping routes

- Modern graphics

- Steering to keep you engaged

I chose to go with each chapter as a real-world location (e.g., Mallorca) that contains multiple routes. You need to complete the previous route to unlock the next one and complete the previous chapter to unlock the next chapter.

I chose Unity3D to create the game. I wanted to have real-world locations, so realistic routes, terrain, and vegetation were a priority. To save time, I used assets from the Unity Asset Store whenever possible.

I used Gaia Pro to create terrains. It handles:

- Generating (stamping) the terrain from a heightmap

- Textures and vegetation spawning based on rules (e.g., spawn trees on flat terrain, rocks on slopes, etc.)

- Dividing the terrain into tiles and managing their loading during gameplay

- Comes with ready-to-use models and textures

To generate roads, I downloaded .gpx files from my Strava activities, then implemented a parser to take coordinates and elevations and build roads in-game using EasyRoads3D. These tools combined worked quite well but required some manual work. I had to go over the entire length of the road to smoothen it up (due to GPS noise in .gpx files). The terrain also didn’t always perfectly align with the road, so I had to manually modify it.

I figured that steering would be a good way to keep the user engaged in the gameplay, instead of just sitting on the bike and pedalling. With required steering, you need to be engaged to not drive off the road.

There are some solutions to virtual steering in other smart trainer games, but they are hardware-based - e.g., for Zwift, you need to buy their hardware controller. I really wanted to keep it as simple and inexpensive as possible, so I used a smartphone mounted to the handlebars as a steering controller.

I implemented native apps for both iOS and Android. They use the gyroscope to get the steering value and broadcast it as a BLE peripheral. Implementing Bluetooth in Unity was a little tricky as there is no built-in solution. The implementation depends on the platform the game is running on. It boils down to writing a native plugin for each platform you support.

For macOS, there is an open-source library written in Swift - https://github.com/codeinversion/sensors-swift. It already has the necessary services and characteristics implemented. I had to modify it a little and compile it into a Unity plugin.

For Windows, there also is a library - https://github.com/adabru/BleWinrtDll, but it wasn’t working too well. Because I targeted UWP, I was able to implement my own Bluetooth logic in C# and compile it directly in Unity.

Overall, it was a really fun project to work on. I’m particularly happy that I was able to release it starting from scratch in just a couple of months, and I hope to continue working on it.